This application is based on and claims priority to Japanese Patent Application No. 11-14704, filed Jan. 22, 1999, the entire contents of which is hereby expressly incorporated by reference.
1. Field of the Invention
The present invention primarily relates to fuel injected engines. More particularly, the present invention relates to a control strategy for controlling a fuel pump of a fuel injected engine after shutdown.
2. Description of the Related Art
Personal watercraft, like other applications that use internal combustion engines as power sources, are experiencing considerable public and governmental pressure to improve not only their performance, but also their exhaust emissions levels. For example, due to the emissions generated by two-stroke powered watercraft, certain recreational areas have banned the operation of such watercrafts. These bans have decreased the popularity of personal watercraft, and have caused manufacturers of these types of watercraft to consider fuel injected engines to power their watercraft and/or other means to reduce emissions levels.
Fuel injected engines are known to provide significantly enhanced performance, power output, and emission control as compared to carbuerated engines. Direct cylinder injection may be accompanied by stratification or lean burning operation to further fuel economy and emission control.
Fuel injection, however, is not easily applied to the engines of personal watercraft. A personal watercraft by its very nature is small and the engine compartment and space for the engine and its auxiliaries is limited. Personal watercraft are generally designed to be operated by a single rider and to carry up to three additional passengers. Thus, not only is the space inside the engine compartment limited but the accessibility of the engine compartment is also limited.
When direct cylinder injection is employed, a high pressure fuel pump is used in order to elevate the fuel to a pressure sufficient for injection into the combustion chambers of the engine, as the pistons in each cylinder approach top dead center (TDC). Direct injection thus requires considerably higher injection pressures than manifold type fuel injection.
Fuel pressures sufficient for direct cylinder injection can be achieved through the use of positive displacement pumps, which are driven mechanically by the output shaft of the engine via a pump drive. The pump drive, however, presents a significant problem in personal watercraft because of the limited space available within the hull.
A need therefore exists for a direct injected engine for a watercraft which operates properly under all operating conditions. For example, it is desirable to provide a direct injected engine for a watercraft which can be stopped and quickly and repeatedly started for short periods of operation.
In accordance with one aspect of the present invention, a fuel injected internal combustion engine comprises an engine body defining at least one combustion chamber. A fuel injector selectively communicates with the combustion chamber to provide a fuel charge to the combustion chamber. A fuel pump supplies fuel to the fuel injector. The engine also includes a controller connected to the fuel pump and configured to operate the fuel pump for a predetermined time period after the engine has been stopped.
For example, the controller continues to operate the fuel pump for the predetermined time period beginning when a user has tripped a kill switch, a lanyard switch or removed a key from a locking ignition switch, although the engine may continue to rotate under its own momentum and/or combustion caused by ignition of residual fuel vapors remaining in the combustion chamber after the engine has been xe2x80x9cstopped.xe2x80x9d Such acts, e.g., tripping a kill or lanyard switch or removing an ignition key, can cause the engine controller to cease spark ignition and/or fuel injection so as to xe2x80x9cstopxe2x80x9d the engine.
By providing the engine with a controller that is configured to operate the fuel pump for a predetermined time period after the engine is stopped, the fuel system of the engine remains primed during the predetermined time period after the engine has been stopped.
It is appreciated that the present fuel injected engine and control strategy has particular utility in marine applications when the engine drives a jet propulsion unit. For instance, when a user is operating a personal watercraft and is approaching a pier or a dock, the user typically maneuvers the watercraft by starting and stopping the engine. The repeated starting and stopping of the engine is effective for docking maneuvers because personal watercraft typically do not have rudders or transmissions with a neutral position. Rather, personal watercraft are usually driven by jet propulsion units which are directly connected to an output shaft of the engine, without the use of a forward, neutral, reverse transmission. In such watercraft, steering forces are generated by directing water from the jet propulsion device at a desired angle, which the rider controls by adjusting a steering nozzle. The propulsion force also is always present when the engine is running.
When a rider decides to dock such a watercraft, the rider typically kills the engine by actuating a kill switch and coasts towards a dock. However, as the watercraft approaches the dock, the user repeatedly starts and stops the engine using a start switch and the kill switch, respectively. In this manner, the rider can slowly and incremental he moved the watercraft closer to the dock as well as steer the watercraft into a docking position. The personal watercraft finally reaches the dock after repeated starts and stops.
An aspect of the present invention involves the recognition that when a conventional engine embodying direct cylinder injection is stopped and the starter button is subsequently depressed, there is a delay created during which the fuel system repressurizes, before the engine can run properly. This delay increases the difficulty of docking maneuvers, making such maneuvers more clumsy and difficult to perform.
For example, high pressure fuel pumps for direct cylinder injected engines typically operate at approximately 50 kg/cm2. When a direct cylinder injection engine is stopped, the fuel pressure on the input side of the high pressure fuel pump drops quickly. As the pressure drops on the input side of the pump, the fuel drains away from the pump, thus allowing the pump to fall quickly into an un-primed state. When such a direct cylinder injected engine is subsequently re-started, a time lag occurs during which the electric fuel pump operates before the high pressure fuel pump is re-primed. This time lag interferes with quick and repetitive stops and efficient restarts of the engine, thus making docking maneuvers more difficult.
By configuring the fuel pump controller to continue the operation of the fuel pump after the engine has been stopped for a predetermined period of time, the high pressure fuel PUMP is prevented to from falling into an un-primed state during such period, thus reducing a time lag associated with re-pressurization of the fuel system when quickly restarted. Therefore, when a user is performing a docking maneuver, the user can stop and restart the engine more quickly and efficiently, thereby making docking maneuvers easier to perform
Further aspects, features, and advantages of the present invention will become apparent from the detailed description of the preferred embodiment which follows.